Enameled sheet steel



SePt- 16, 1930. H. c. HARVEY 1,776,116

ENAMELED SHEET STEEL Filed Jan. 1i, 192s Wl- Wifi-E f d @0000009 'd @AGML W I TN ESS INVENTOR ATTORNEYS Patented Sept. 16, 1930 UNITED STATESPATENT OFFICE HAROLD G. HARVEY, 0F TRENTON, NEW JERSEY, ASSIGNOR TO THEAGASOTE MILL- -BOARD COMPANY, OF EWING TOWNSHIP, NEW JERSEY, ACORPORATION OF NEW JERSEY i ENAMELED SHEET STEEL Application led January11, 1928. Serial No. 246,068.A

My invention relates to sheets of enameled steel of such size, relativeto their thickness, that they will ordinarily assume a curved shapeduring the manufacture thereof, and has for its object the provision ofcertain means for overcoming in whole, or to a large part, the tendencyto assume such curved shape. Enameled steel treated in accordance withmy invention ma be used for many purposes, for instance,airies',bathrooms, kitchens, pantries, restaurants, the lining of rail-vroad cars, tunnels, etc.

Enameled sheet steel is well known in the art of steel treatment. As isknown to those skilled in the art, steels of a special type are used forthis purpose which are ysubjected to x a stretching operation and apreliminary surfacing operation (ground coating). The enamel powder isthen placedupon the steel so treated and fused thereon in a kiln orfurnace heated to a temperature suficient for this purpose, usually inthe neighborhood of 2500 F. When the steel is thereafter cooled it isobtained in a distorted form, if it is of such size that its inherentstrength is insuicient t'o overcome the tendency to become distorted.Comparatively small sheets even of relatively thin steel, and sheets oflarger size, but thicker steel, will not be distorted to any substantialdegree. But a sheet, for'instance, ten feet long, four feet wide, and ofa thickness indicated by gauges 18 to 4() will assume a curved formduring the process of manufacture. It is this type of sheet that I referto in m yclaim as enameled steel of the kind w ose normal shape iscurved, and whose treatment I` describe below. If the sheet is oblong itwill take a curve along its minor axis, the major axis lyingsubstantially in a straight line, while if it is square or very nearlyso it will generally curve into dish form.

My invention'involves the step of so-shaping certain portions of thesteel sheet prior to the application of the enamel and the subsequentheat treatment, and in such a manner and along such lines that suchportions con-f bracing means I designate in my claim as integral bracingmeans. Just where such bracing means must be applied can easily bedetermined by a study of the curved steel and ifnecessary by theempirical method of sucv cessively supplying bracing means until thedesired degree of stiness in the enameled sheet is attained. Inpractice, however, I prefer to use such bracing means not only for theirmechanical effect but also for their ornamental effect and may thereforeapply more of suchmeans than might be necessary fori attaining thedesired mechanical eect on y.

In the accompanying drawing illustrating several forms of my invention,Fig. 1 shows a plan view of a sheet of enameled steel having formedintegrally therewith longitudinal and transverse bracing means to resistthe bending stresses in said steel in accordance with my invention;Figs. 2, 3 and 4 are views similar to Fig. 1 but illustrating a numberof different ornamental effects ,that may be attained in addition to themechanical effect by the practice of my invention; Fig. 5 shows anoblong plate having bracing means embodied therein designed primarily toprevent distortion of the sheet; Fig. 6 is a sectional view taken alongthe line 6-6 of Fig. 1.

Referring to the drawings, a represents a sheet ofenameled steel of anydesired shape, but generally square or oblong, the letter b indicatingthe base plate of steel and c the enamel coating thereon.` Bracing meansd, which may be in the form of corrugations or ribs or other compressedand shaped sect-ions, are formed integral with the body of the steelsheet, and extend in such directions and are formed in such number as toovercome partially or entirely, as desired, any tendency of the sheet ofenameled steel to curve in any direction ldue to stresses `set up duringthe manufacturing operations.

The form of indentations or ribs shown is that produced by a shallowarcuate groove or trough, but it is obvious that dierent depths ofribsmay be employed and that other shapes of integral strengthening ribswill suggest themselves to those skilled in the art.

I shall now describe the preferred manner of practising my invention foruse in making a sheet of enameled steel having a substantially fiatform.

From among a batch of steel sheets or plates which are to receive acoating of enamel, and which are preferably of substantially the samegauge, shape and chemical composition and which have been produced undersubstantially similar conditions, so as to react similarly to thevarious treatments to which they are subjected prior, during and afterthe enameling operation, I take a sample sheet and give it the necessarypreliminary treatment such as stretching, ground coating, etc. which arewell known to those skilled in the art of enameling steel, and afterapplying the enamel powder thereto, subject it in a furnace or oven to asufficiently high temperature to fuse the enamel thereon to form asmooth homogeneous coating. The sheet is then cooled, after which it iscarefully examined to determine the extent of the distortion of theenameled sheet. The number, location, sharpness (i. e. curvature) anddirection of the curves are noted.

From these data, the length, direction, location and depth or strengthof the bracing ribs to be formed on the steel sheets prior to theenameling operations so as to overcome the bending stresses set up inthe steel sheets during the enameling and cooling operations, can beapproximately determined by inspection. The bracing means shouldgenerally run in a direction substantially at right angles to the axesof the curved surfaces noted on the sample sheet and should preferablyextend completely across the surfaces indicated by the sample sheet ascertain'to be curved after said enameling and cooling operations. If thecurved surface is bounded by a more or less plane or flat surface therib or other bracing means should preferably extend at least partiallyacross said plane surface to insure more effective stiffening of theplate or sheet. Where the curvature is smaller (i. e. the radius of thecurve is large), shallower or fewer ribs will be necessary, whereaswhere the curve is sharper (i. e. the radius is small), deeper or moreribs will be necessary to prevent curving of the sheet.

Having thus determined from a st-udy of the distortion of the samplesheet approximately the minimum amount of bracing necessary to insurethat the finally cooled enameled sheet shall be of a substantially fiatform, I take a second sample sheet and preferably before the. groundcoating treatment, but after the stretching operation if suchpreliminary treatment is employed, form in the body thereof, as bystamping or pressing,

bracing ribs or corrugations of a length, depth and direction determinedby such study of the first sample sheet. I then ground coat and finallyenamel and cool the said second sample sheet in the well-known manner.If this latter sheet emerges in substantially Hat form from the coolingapparatus, it will be clear that it has been braced either justsuiiiciently or too much to overcome the bending stresses in the steel.If an excess in the number or depth or length of the ribs is notobjectionable then no further study and trial need be made and the restof the batch of plates can be stamped or pressed and enameled in thesame way as the second sample sheet.

If, however, it is desirable to have as few ribs or as short or asshallow ribs as possible,

then it may be assumed that the said second sample sheet has been giventoo much bracing, and a third sheet may then be taken and given the sametreatment except that the ribs may be made shallower, and/or shorterand/or fewer in number. If the finally finished cooled sheet is stillflat in shape, a fourth sample sheet may be employed and similarlytreated but given weaker stitl'ening means and this trial methodcontinued until a safe minimum of bracing ribs, allowing for possiblevariations in the steel plates, is found.

Of course, instead of making these trials one at a time, a number ofsample sheets may be treated simultaneously, being given stifteningmeans of different degrees of strength, the safe minimum beingdeterminedfrom a study of the finally cooled sheets.

If the second sample sheet, above referred to, instead of being heldflat by its bracing ribs, is still curved, other sample sheets are takenand similarly treated but given stiflfening means of increasing strengthuntil a safe minimum is determined.

For many of the uses to which my enamin the form of geometrical designs,though other designs will occur to those skilled in the art ofornamentation. In Fig. 1 I show longitudinal and transverse ribsintersecting to form rectangles. In a sheet of this oblong form, thelongitudinal strengthening ribs are not quite as necessary as thetransverse ribs because the sheet, when enameled and cooled, tends tocurve along its minor axis. In Fig. 2 I have therefore weakened tl'eselongitudinal ribs to obtain the more decorative tile effect. Fig. 3shows a sheet having ribs intersecting and forming squares, there beingmore longitudinal and transverse ribs than are necessary to insureflatness. In Fig. 4 I have weakened the longitudinal and transverse.

components of the ribs by impressing them into the sheet at an angle tothe latters axes thereby producing the ornamental diamondshape design.Fig. 5 shows a design that may be followed When a minimum amount ofbracing is desired.

If desired the enamel covering the indentations or ribs may be of adifferent color :from that of the rest of the sheet in order to in#crease the ornamental efect.

My invention may also be employed to obtain sheets of enameled steelhaving a definite' curvature of larger radius than that of normalcurvature of the unbraced sheet. In the practice of this form of myinvention, the sheets are stifened by means of ribs or corrugationswhich are insuicient to overcome completely the bending stresses createdduring the cooling operation.- The exact length, depth, direction andlocation of these stiieningr means which Will permit the sheet to remainsomewhat curved, may be determined by the empirical method outlinedabove in connection with the production of flat sheets of enameledsteel.

It will be obvious, that where a sheet curves along more than one arc,as Where a sheet leaves the cooling apparatus in dished, shape, and itis desired to retain the curvature along one arc, the strengthening ribsmay be so directed and located (as may be determined empirically) as toovercome the tendency to curve along all arcs but the desired one.

I Wish it to be understood that where in the claim I employ theexpression substantially at I mean to y'include thereby all shapes whichare substantially nearer the flat condition than is the normal shape ofthe unbraced sheet of enameled steel.

When I refer in my claim to steel, I desire i it to be understood thatsuch term includes not only steel but any other metallic material, suchas iron, which has a curved form after enameling, whether or not it hasbeen subjected to the particular treatment of stretching and scribed.

I claim:

ground coating hereinabove de- The method of making a substantially flati sheet of enameled steel Which consists in applying to a sheet of steelof such dimensions that during the process of baking enamel thereon itwould assume, and thereafter retain, the form of a curve, indentationsconstituting integral bracing means crossing the lines which would formthe axes of such curve, and then baking a coating of enamel thereon. f

HAROLD C. HARVEY.

